As is well known, rubber molding compositions require both elevated temperatures and elevated pressures in order to achieve vulcanization or cure; and in the past, the elevated pressure for the molding of rubber parts has been ordinarily supplied by electrically energized hydraulic systems. However, these prior art hydraulic presses operate under maximum system pressure with the highest energy consumption when the dies are closed; and that latter condition exists for perhaps 90% of the molding cycle. In addition to being energy-inefficient, hydraulic molding presses are restricted in the pressures that can be delivered for a given operating cycle; and these presses have the additional disadvantage of being incapable of control within narrow limits of pressure and cycle time.